Stjörnukerfi

Stjörnukerfi is the Icelandic term for the solar system, the gravitationally bound system that includes the Sun and the objects that orbit it—planets, dwarf planets, moons, asteroids, comets, and other small bodies. It formed about 4.6 billion years ago from the collapse of a giant molecular cloud. The Sun contains about 99.8 percent of the system’s mass, and its gravity governs the orbital motions of all members. The major planets orbit the Sun on relatively stable, near-circular paths and are commonly divided into two groups: the inner terrestrial planets (Mercury, Venus, Earth, Mars) and the outer gas and ice giants (Jupiter, Saturn, Uranus, Neptune).

In 2006 Pluto was reclassified by the International Astronomical Union as a dwarf planet, part of the broader population of icy bodies in the outer solar system. Beyond the eight planets lies the asteroid belt between Mars and Jupiter, and farther outward the Kuiper belt and the scattered disc, which host many small icy bodies. The Oort cloud is a theoretical sphere of distant comets believed to surround the Sun at the edges of the solar system.

The stjörnukerfi has been studied through telescopic observations and space missions from many space agencies. Notable missions include Voyager probes, the Cassini–Huygens mission to Saturn, the New Horizons flyby of Pluto, and numerous missions to the planets and their moons. The system serves as a primary example for theories of planetary formation, orbital dynamics, and the evolution of small-body populations.